Pthread Posix素因子化得到奇怪的结果？

Question

我有这个项目，我从命令行接收输入，如“54 342 12”，它假设为每个输入创建一个线程，并让线程返回一个整数数组，然后主线程支持打印输出不同的主要因素分解。但我收到奇怪的输出，如一堆零。我不知道为什么，任何帮助将不胜感激。

#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>


typedef struct _thread_data_t {
        int tid;
        } thread_data_t;

void *runner(void *param);

int main(int argc, char *argv[]) {

        pthread_t thr[argc];
        pthread_attr_t attr;
        int i, rc;
        //int *primeFactor;
        //primeFactor = (int *)malloc(sizeof(int)*argc);
        //thread_data_t thr_data[argc];
        printf("Prime Numbers: ");

        //Get the default attributes
        pthread_attr_init(&attr);
        //creat the thread
        for(i = 1; i < argc; ++i){
        //thr_data[i].tid = i;
        if ((rc = pthread_create(&thr[i],&attr,runner,argv[i]))){
                fprintf(stderr, "error: pthread_create, rc: %d
", rc);
                return EXIT_FAILURE;
                }
        }

        //Wait for the thread to exit
        for(i = 1; i < argc; ++i){
        void *returnValue;
        int r = 0;
        int x = (sizeof(returnValue) / sizeof(returnValue[0])) - 1;
        pthread_join(thr[i], &returnValue);
                for(r = 0; r < x; r++){
                //int c = (int *)returnValue[r];
                printf("%d ",  ((int *)returnValue)[r]);
                }
        }
        printf("
Complete
");

}

//The Thread will begin control in this function
void *runner(void *param) {
        int *primeFactors;
        int num = atoi(param);
        primeFactors = (int *)malloc(sizeof(int)*num);
        int i, j, isPrime;
        int k = 0;
        for(i=2; i<=num; i++)
        {
                if(num%i==0)
                {
                        isPrime=1;
                        for(j=2; j<=i/2; j++)
                        {
                                if(i%j==0)
                                {
                                        isPrime = 0;
                                        break;
                                }
                        }

                        if(isPrime==1)
                        {
                                primeFactors[k] = i;
                                k++;
                        }
                }
        }


        //Exit the thread
//      pthread_exit(0);

//      pthread_exit((void *)primeFactors);
        pthread_exit(primeFactors);
}